Photoperiod regulates elicitation of growth promotion but not induced resistance by plant growth-promoting rhizobacteria

Abstract

For several years, we have noticed that plant growth-promoting rhizobacteria (PGPR), which consistently promote plant growth in greenhouse tests during spring, summer, and fall, fail to elicit plant growth promotion during the midwinter under ambient light conditions. This report tests the hypothesis that photoperiod regulates elicitation of growth promotion and induced systemic resistance (ISR) by PGPR. A commercially available formulation of PGPR strains Bacillus subtilis GB03 and Bacillus amyloliquefaciens IN937a (BioYield) was used to grow tomato and pepper transplants under short-day (8 h of light) (SD) and long-day (12 h of light) (LD) conditions. Results of many experiments indicated that under LD conditions, BioYield consistently elicited significant increases in root and shoot mass as well as in several parameters of root architecture. However, under SD conditions, such increases were not elicited. Differential root colonization of plants grown under LD and SD conditions and changes in leachate quality partially account for these results. BioYield elicited ISR in tomato and pepper under both LD and SD conditions, indicating that although growth promotion was not elicited under SD conditions, induced resistance was. Overall, the results indicate that PGPR-mediated growth promotion is regulated by photoperiod, while ISR is not.

Plant Growth Promoting Rhizobacteria (PGPR) Reduces Application Rates of Fertilizers in Chili (Capsicum frutescens L.) Cultivation

“…Shaharoona et al [9] testified in wheat N use proficiency improve in reply to inoculation with Pseudomonas fluorescens. From the previous works, the PGPR performance increase with co-inoculation with several PGPR strains [19,15,10,11]. For example, Belimov et al [19] stated co-inoculation of Arthrobacter mysorens 7 and Azospirillum lipoferum 137 or Agro bacterium 10 and Azospirillum lipoferum 137 give results significantly maximum uptake of phosphorus P in shoot of barley.…”

“…For the achievement of these objectives, experiments were planned using different levels of fertilizer with or without formulated PGPR product. The PGPR were formally disclosed to stimulate significant effects on plant growth, yield and root development [10][11][12][13].…”

Plant growth promoting rhizobacteria and their potential for biocontrol of phytopathogens

“…Thus, rhizosphere has a versatile and dynamic ecological environment of intense plant-microbe interactions (Mayak et al, 2004) harnessing essential micro and macronutrients affecting plant growth; although, the process of root colonization is under the influence of various parameters such as bacterial traits, root exudates and several other biotic and abiotic factors (Benizri et al, 2001). PGPR can alter root architecture and promote plant development with the production of different phytohormones like IAA, gibberellic acid and cytokinins (Kloepper et al, 2007). Several PGPRs as well as some pathogenic, symbiotic and free living rhizobacterial species are reported to produce IAA and gibberllic acid in the rhizospheric soil and thereby play a significant role in increasing the root surface area and number of root tips in many plants (Han et al, 2005).…”

Potency of Bacillus spp from Potato Rhizosphere as Active Ingredients for Biostimulant Formulation

“…Bacteria are the most abundant microorganisms in the rhizosphere, most likely to affect plant physiology, especially through plant rooting colonization (Kloepper, 2007). Rhizospheric bacteria that colonized rooting play an important role in the regulation of plant growth triggers known as plant growth promoting rhizosphere (PGPR) (Kloepper et al, 1980).…”